10-12 torr with a getter might be able to get rid of free oxygen, but not bonded oxygen. And you possibly have to wait a long time in order for the getter to get all of the oxygen out of your chamber (provide no leak). My 2 cents. Is it how you test your chamber of XPS? Pump down for long time, check oxygen peak on copper (clean, sputtered to almost no oxygen, leave it over night and check if any oxygen back to the surface, if you got a small peak, check it again after bake. Painful process).
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Sunday, April 14, 2013 02:42 PM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Pakeout and PCB Separators
Oxidation...Oxygeg.question for Bob: Remember our little discussion on
'zero' . What I ask now has no practical application. I have had the
thought before when I used ultrahigh vacuum (exp -12)..Now to question: Is
it possible to remove all oxygen molecules in a volum made of xxxxx. I mean
zero molecules, not one single molecule. Or is there a place in Universe
where a Oxygen atom is unthinkable?
Inge
On 10 April 2013 16:54, Robert Kondner <[log in to unmask]> wrote:
> I will agree about oxidation but not faster drying. I mean the vapor
> pressure of water is already quite low at room temperature. I think drying
> time for a material with absorbed vapor is fixed by diffusion rates and
> distance. And temperature is a bit driver of diffusion rate. Is air
> pressure
> even in the equation?
>
> Bob K.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
> Sent: Tuesday, April 09, 2013 2:12 PM
> To: [log in to unmask]
> Subject: Re: [TN] Pakeout and PCB Separators
>
> Baking in Vacuum oven = less pads oxidation and faster drying
>
>
> On Tue, Apr 9, 2013 at 9:00 PM, Glidden, Kevin
> <[log in to unmask]>wrote:
>
> > Someone in Technet not long ago posted up an excellent little write up
> > from Gordon Davy about water vapor and drying. I've attached it to
> > Phil and Bob.
> >
> > It contends vacuum ovens do nothing to increase drying rate.
> >
> > Drying is a function of temperature and delta between concentration of
> > water in the middle versus at the surface.
> >
> > I presume, like any drying, the greater the surface area exposed the
> > faster the drying. I would place the PCBs (as much as possible)
> > directly on racks or in card holders (on edge).
> >
> > -----Original Message-----
> > From: Nutting, Phil [mailto:[log in to unmask]]
> > Sent: Tuesday, April 09, 2013 1:01 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Pakeout and PCB Separators
> >
> > Robert,
> >
> > How about placing them in a vacuum chamber. That would release all
> > the moisture and definitely if you could add a little heat. I would
> > envision separating the boards with a mesh and spacer to allow the
> > moisture to fully escape. Placing a paper towel between layers might
> > not let all the moisture escape.
> >
> > But then this is just my opinion.
> >
> > Phil Nutting
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> > Sent: Tuesday, April 09, 2013 12:54 PM
> > To: [log in to unmask]
> > Subject: [TN] Pakeout and PCB Separators
> >
> > Hi,
> >
> >
> >
> > Does anyone know if separators of some type between PCBs can reduce
> > bake out time?
> >
> >
> >
> > If I have a stack of PCBs, and I place something like paper towels
> > between PCBs, can the bake out time be reduced? I would imagine the
> > diffusion rates of moisture in the paper towel material would be much
> > higher than in solid PCB laminate. But, that is just a guess. Could be
> perfect hog wash.
> >
> >
> >
> > My problem is not with PCBs but with 30 mil sheets of plastic that
> > feed a thermoforming process. I am using PETG but I still see small
> > bubbles in the material after forming. I tried a short bake out, and
> > it helps, but I cannot heat very high as the 30 mil plastic sheets
> > will easily deform. I need to lay them flat, heat gently, and still
> > try to removed moisture. I was wondering what the best way to separate
> > sheets and allow drying might be.
> >
> >
> >
> > Any Ideas?
> >
> >
> >
> > Thanks,
> >
> > Bob K.
> >
> >
> >
> >
> >
> > ______________________________________________________________________
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> --
>
> Best Regards,
>
> *Reuven Rokah*
>
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